Jump to content


Photo

Nice Double-Double near M81

  • Please log in to reply
9 replies to this topic

#1 Cotts

Cotts

    Just Wondering

  • *****
  • Posts: 4780
  • Joined: 10 Oct 2005
  • Loc: Toronto, Ontario

Posted 20 April 2014 - 06:32 PM

Observing with my TEC 140 on Saturday night, April 19th...

There is a very nice 'Double Double" about 10-11 arcmin SSW of the center of M81. They are in the WDS as STF 1387 and STF 1386.

The pair closer to the nucleus of M81 is STF 1387, mags 10.44 and 10.73, separation 8.9"

The more southerly pair (and thus further from M81), by about 130" is STF 1386, mags 8.73, 9.34, separation 2.0".

I had a very nice view and split of both with my new TEC 140 and a 5mm Nagler (196 power). The close pair is difficult with this aperture due to the combination of its closeness and faintness. It is possible to get the galaxy and both pairs in one field of view.....

Dave

#2 WRAK

WRAK

    Apollo

  • -----
  • Posts: 1140
  • Joined: 18 Feb 2012
  • Loc: Vienna, Austria, Europe

Posted 21 April 2014 - 03:34 AM

Nice to read here after some time again a post about an interesting observation. Had these doubles already in my raw listing of interesting targets in UMa but was not aware that this is a double-double. WDS even lists an STF1386 AB,CD object with CD for STF1387 - although proper motion does not suggest this might be a physical double-double.

UMa is for spring and early summer an especially interesting field of view to keep in mind for clear nights with a bright moon - much better to have the headlights from behind making thus despite the bright sky a decent double star session possible.
Wilfried

#3 desertstars

desertstars

    ISS

  • *****
  • Posts: 42766
  • Joined: 05 Nov 2003
  • Loc: Tucson, AZ

Posted 21 April 2014 - 06:43 PM

I've added these to my checklist for the next night out.

#4 fred1871

fred1871

    Viking 1

  • -----
  • Posts: 850
  • Joined: 22 Mar 2009
  • Loc: Australia

Posted 21 April 2014 - 11:42 PM

They're quite a neat combination, especially with a bit more aperture. Back when I was north of the equator I came across this double pairing, nicely offset beside M81. Viewed with a C8 at 80x the dimmer wider pair was obvious, and the close pair barely separated; 135x gave a neat view of both with the closer pair a good split at that power. I think the extra light of 200mm vs 140mm helped.

Cotts, interesting that your quoted magnitudes don't match the WDS listing. Are these Sky Safari numbers?

#5 Cotts

Cotts

    Just Wondering

  • *****
  • Posts: 4780
  • Joined: 10 Oct 2005
  • Loc: Toronto, Ontario

Posted 22 April 2014 - 06:21 AM

They're quite a neat combination, especially with a bit more aperture. Back when I was north of the equator I came across this double pairing, nicely offset beside M81. Viewed with a C8 at 80x the dimmer wider pair was obvious, and the close pair barely separated; 135x gave a neat view of both with the closer pair a good split at that power. I think the extra light of 200mm vs 140mm helped.

Cotts, interesting that your quoted magnitudes don't match the WDS listing. Are these Sky Safari numbers?


Yes, Fred, they are from Sky Safari - I tried to get the WDS data but, apparently, the site is still down... (tried it just now - 404 not found...)

I think the mags from Sky Safari are too bright for the closer pair - they seemed to be fainter than the wide pair..... I guess we wait until WDS wakes up....

Dave

#6 fred1871

fred1871

    Viking 1

  • -----
  • Posts: 850
  • Joined: 22 Mar 2009
  • Loc: Australia

Posted 22 April 2014 - 09:21 AM

Dave, yes, you're quite correct about STF 1386 being less bright than Sky Safari suggests - the WDS magnitudes for the closer pair are 9.30 and 9.34, which suggests that Sky Safari is listing the combined magnitude as the number for star A, and then giving the correct figure for star B. There's a similar pattern for STF 1387, but there the numbers don't add up, so it's some kind of muddle.

I download a copy of the current WDS from time to time, so I have a reference copy on my computer, and don't depend on the vagaries of the internet. The catalog doesn't change rapidly, given its size, so much of the data is the same for extended periods of time; that's especially true for photometry.

#7 WRAK

WRAK

    Apollo

  • -----
  • Posts: 1140
  • Joined: 18 Feb 2012
  • Loc: Vienna, Austria, Europe

Posted 22 April 2014 - 11:42 AM

Thought the SkySafari double star magnitude issue as solved with version 4 (including now the complete WDS catalog) - but is obviously not.
Wilfried

#8 ssmith

ssmith

    Vostok 1

  • *****
  • Posts: 118
  • Joined: 28 Jun 2012
  • Loc: Colorado

Posted 22 April 2014 - 11:59 PM

I went back and looked at the photos I took of the supernova in M82 back in January and saw that I had captured both doubles in the FOV but obviously did not split STF 1387 with my 80mm scope. Attached is a cropped view of M81 and the doubles.

Attached Files



#9 WRAK

WRAK

    Apollo

  • -----
  • Posts: 1140
  • Joined: 18 Feb 2012
  • Loc: Vienna, Austria, Europe

Posted 23 April 2014 - 01:25 AM

Great picture. While STF1386 is not resolved it shows a hint of an horizontal elongation - corresponding rather well to the PA of 111°.
Wilfried

#10 R Botero

R Botero

    Apollo

  • -----
  • Posts: 1228
  • Joined: 02 Jan 2009
  • Loc: Kent, England

Posted 24 April 2014 - 05:25 AM

Great shot indeed! :cool: :bow:






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics